Java program for longest palindrome in an array
Longest Palindrome in an Array in Java
Here, in this page we will discuss the program to find the longest palindrome in an array in java programming language. We are given with an array and need to print the longest palindromic element in the given input array.

Method Discussed :
- Method 1 : Using Naive Approach
- Method 2 : Using Sorting
Method 1 :
- Create a function ispalindrome(int n), it will return 1 if the passing number is palindrome otherwise return 0.
- Inside the main function, create a variable say res = -1, that hold the maximum palindrome number.
- Run a loop from [0, n), and check if(ispalindrome(arr[i]) && res<arr[i]), then set res = arr[i].
- Print the value of res.
Method 1 : Code in Java
Run
import java.util.*; class Main { // Function to check if n is palindrome static boolean isPalindrome(int n) { // Find the appropriate divisor // to extract the leading digit int divisor = 1; while (n / divisor >= 10) divisor *= 10; while (n != 0) { int x = n / divisor; int y = n % 10; // If first and last digits are // not same then return false if (x != y) return false; // Removing the leading and trailing // digits from the number n = (n % divisor) / 10; // Reducing divisor by a factor // of 2 as 2 digits are dropped divisor = divisor / 100; } return true; } // Function to find the largest palindromic number static int largestPalindrome(int []A, int n) { int res = -1; for (int i = 0; i < n; i++) { // If a palindrome larger than the currentMax is found if (A[i] > res && isPalindrome(A[i])) res = A[i]; } // Return the largest palindromic number from the array return res; } // Driver program public static void main(String []args) { int []A = { 121, 2322, 54545, 999990 }; int n = A.length; // print required answer System.out.println(largestPalindrome(A, n)); } }
Output
54545
Method 2 :
In this method we first sort the array and then start traversing the array from end, and return the element that satisfy the condition, that it is palindrome.
- Sort the array using inbuilt sort() function.
- Start traversing from end of the array,
- Print the element if it is palindrome.
- If no element found then print -1.

Method 2 : Code in Java
Run
import java.util.*; class Main { // Function to check if n is palindrome static boolean isPalindrome(int n) { // Find the appropriate divisor // to extract the leading digit int divisor = 1; while (n / divisor >= 10) divisor *= 10; while (n != 0) { int x = n / divisor; int y = n % 10; // If first and last digits are // not same then return false if (x != y) return false; // Removing the leading and trailing // digits from the number n = (n % divisor) / 10; divisor = divisor / 100; } return true; } // Function to find the largest palindromic number static int largestPalindrome(int []A, int n) { Arrays.sort(A); for (int i = n-1; i >= 0; i--) { // If a palindrome larger than the currentMax is found if (isPalindrome(A[i])) return A[i]; } // Return the largest palindromic number from the array return -1; } // Driver program public static void main(String []args) { int []A = { 121, 2322, 54545, 999990 }; int n = A.length; // print required answer System.out.println(largestPalindrome(A, n)); } }
Output
545545
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public class LongestPalindrome {
public static void main(String[] args) {
int[] arr = { 121, 2322, 54545, 5454545, 999990 };
int max = 0;
for(int i=0; i<arr.length; i++) {
int rem, reverse = 0;
int temp = arr[i];
while(temp != 0) {
rem = temp % 10;
reverse = reverse * 10 + rem;
temp /= 10;
}
if(reverse == arr[i] && max < arr[i]) {
max = arr[i];
}
}
if (max == 0) {
System.out.println("No palindrome found");
} else {
System.out.println("The largest palindrome number is: " + max);
}
}
}